1. Field of the Invention
This invention relates to image reading equipment for an image recording apparatus, such as a digital copying machine, facsimile machine, or printer, and more particularly to a self-diagnostic system for such image reading equipment wherein such a system is capable of performing a source of error in a plural number of circuit boards in the image reading equipment easily and in a short time.
2. Description of the Related Art
In a conventional copying machine, which is discussed here as an example of image recording equipment, an original sheet is illuminated with a beam of light from a lamp and an image of the original is formed on a photosensitive drum or a photosensitive belt by way of an adequate optical system, to form a latent image. Hence, such image reading equipment consists of a lamp and its scanning system and/or an optical system. Therefore, in the event that a problem has developed in such image reading equipment, it is consequently sufficient to perform tests on the conduction of the lamp or checks on the on/off operations of the lamp, checks on the scanning system, and checks on the optical system.
In recent years, however, efforts have been made to attain higher image quality and to realize multiple functions through effective utilization of highly advanced controlling techniques and image data processing techniques made possible by the introduction of a computer system into such image recording equipment as copying machines, facsimile machines, and printers, and, specifically for image reading equipment as such, it has been extensively in practice to decompose the images on the original sheet into electric signals by means of a line sensor comprised of CCD, etc., to digitalize such signals and to perform the desired image processing operations.
Therefore, in case a problem has occurred in the image reading equipment, it is necessary to judge whether it is a problem in the line sensor or a problem in the circuit for processing video signals at a succeeding stage. In order to do so, it is necessary to measure the video signals in the various parts of the circuit, using a measuring instrument such as an oscilloscope, and yet there are problems in that it is quite troublesome to take an oscilloscope along for servicing and that well-developed skills and time are required for such services.
On the other hand, it is desired to reduce the servicing time. The shorter the servicing time is, the shorter the downtime of the machine will be, and this is desirable from the user's viewpoint, and when the servicing time can be reduced while satisfying the servicing needs, the number of the machines on which one serviceman can perform maintenance jobs will be increased, with the result that the servicing costs as a whole can be thereby reduced considerably.